CN112892236B

CN112892236B - High-strength polyethylene composite membrane for water treatment and preparation method thereof

Info

Publication number: CN112892236B
Application number: CN202110256728.0A
Authority: CN
Inventors: 翁星星; 刘涛涛; 沈亚定; 盛夏
Original assignee: Jiangsu Housheng New Energy Technology Co Ltd
Current assignee: Jiangsu Housheng New Energy Technology Co Ltd
Priority date: 2021-03-09
Filing date: 2021-03-09
Publication date: 2022-04-22
Anticipated expiration: 2041-03-09
Also published as: CN112892236A

Abstract

The invention discloses a high-strength polyethylene composite membrane for water treatment and a preparation method thereof. The polyethylene composite film comprises a microporous polyethylene film, polyvinyl alcohol/bacterial cellulose and L-cysteine. Has the advantages that: (1) the polyvinyl alcohol/bacterial cellulose is used for modifying the microporous polyethylene film, so that the heat resistance, the water resistance and the mechanical strength of the polyethylene composite film are improved; (2) the polyvinyl alcohol/bacterial cellulose is prepared by a microwave reaction method, so that the reaction time is reduced, and the polyvinyl alcohol/bacterial cellulose has a more uniform and more detailed cross-linking structure; (3) the polyvinyl alcohol/bacterial cellulose is modified by utilizing micromolecular acryloyl chloride, so that the surface roughness of the polyethylene composite membrane is reduced, and the smoothness of the membrane is increased, so that the attachment of pollutants is reduced; (4) l-cysteine is grafted on the polyethylene composite membrane by utilizing thiol reaction, so that the reaction of active amino and carboxyl is effectively inhibited, and the antifouling property of the membrane is improved.

Description

High-strength polyethylene composite membrane for water treatment and preparation method thereof

Technical Field

The invention relates to the technical field of water treatment, in particular to a high-strength polyethylene composite membrane for water treatment and a preparation method thereof.

Background

Since the new century, the progress of social urbanization has been intensified, so that the problem of water pollution caused by human activities is more serious. Industrial, agricultural and domestic untreated wastewater discharge pollutes surface water and underground water, limits direct access of fresh water resources to humans, and membrane separation technology is one of the most effective technologies considered to solve the problem. Among them, the ultrafiltration membrane is a membrane having high mechanical strength and good chemical stability and used for water treatment. However, the water body treated generally contains protein pollution, which easily causes the attachment of the pollutant, causes the function reduction of the membrane, reduces the water treatment efficiency and the water treatment quality, and has short service life.

At present, most of water treatment membranes are compounded by polyester non-woven fabrics, polyla and polyamide, so that the cost is high and the process is complex. Alternative products with simple process and lower cost are urgently needed. The microporous polyethylene membrane is widely used for the battery diaphragm due to adjustable pores, excellent mechanical property and chemical stability, is a main body of a potential water treatment membrane, but is rarely used for water treatment, and is easy to cause mechanical capacity reduction due to hydrophobicity after long-term operation in a water environment, so that the durability is low, and the service life is short; and the residue of pollutants is easy to block the pore channel when the filter is used for a long time; therefore, a series of improvements in treatment methods are required to increase hydrophilicity, water resistance, and antifouling property so that they can be used for water treatment.

In conclusion, the preparation of the high-strength polyethylene composite membrane for water treatment is of great significance.

Disclosure of Invention

The invention aims to provide a high-strength polyethylene composite membrane for water treatment and a preparation method thereof, so as to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme:

a high-strength polyethylene composite film for water treatment comprises a microporous polyethylene film, polyvinyl alcohol/bacterial cellulose and L-cysteine.

Preferably, the polyvinyl alcohol/bacterial cellulose is prepared by using tartaric acid as a cross-linking agent and adopting a microwave reaction method.

Preferably, the thickness of the polyethylene composite film is 150-300 μm.

Preferably, the preparation method of the high-strength polyethylene composite membrane for water treatment comprises the following steps:

step 1: preparation of a solvent: obtaining a solution A from the PVA solution and the bacterial cellulose solution for later use; mixing a sulfuric acid solution and a tartaric acid solution to obtain a solution B for later use; mixing a triethylamine solution, a hydroquinone solution and a sodium dodecyl sulfate aqueous solution to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D for later use; dissolving L-cysteine and potassium persulfate in a buffer solution to obtain a solution E for later use;

step 2: preparing a polyethylene composite film: soaking the microporous polyethylene membrane in an ethanol solution, transferring the microporous polyethylene membrane to a cross-flow membrane filter, and circularly filtering for 8-12 minutes by using the solution A; taking out and transferring the solution to a solution B, adjusting the pH value of the solution to be 3 by using an acidic catalyst, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, filtering, washing and drying to obtain a composite membrane A; transferring the mixture into a solution C, dropwise adding a solution D, and setting the temperature to be 50 ℃ for reaction after the dropwise adding is finished; and taking out and transferring the solution to the solution E, setting the temperature to be 60 ℃ for reaction under vibration, washing and filtering to obtain the polyethylene composite membrane.

Preferably, the specific process of step 1 is as follows: mixing the PVA solution and the bacterial cellulose solution according to the volume ratio of 2:1, and stirring for 1-1.5 hours at the temperature of 90-95 ℃ to obtain a solution A for later use; mixing a sulfuric acid solution and a tartaric acid solution in equal volume, and stirring for 40-45 minutes at the temperature of 25-30 ℃ to obtain a solution B for later use; mixing a triethylamine solution, a hydroquinone solution and a sodium dodecyl sulfate solution in equal volume to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D for later use; dissolving L-cysteine and potassium persulfate with the mass ratio of (12-13): 1 in a buffer solution to obtain a solution E for later use;

optimally, the concentration of the PVA solution is 0.5-1 wt%; the concentration of the bacterial cellulose solution is 0.4-0.6 wt%; the concentration of the sulfuric acid solution is 5-8 wt%; the tartaric acid solution accounts for 0.25-0.3 wt%; the concentration of the triethylamine is 1-3 wt%; the concentration of the hydroquinone solution is 2-4 wt%; the concentration of the sodium dodecyl sulfate solution is 0.1-0.2 wt%.

Preferably, the concentration of the solution D is 1-2 wt%; the concentration of the solution E is 20-25 wt%.

Preferably, the specific process of step 2 is as follows: soaking the microporous polyethylene membrane in an ethanol solution for 10-15 minutes, transferring to a cross-flow membrane filter, setting the temperature to be 20-25 ℃, setting the pressure to be 5bar, and circularly filtering for 8-12 minutes by using the solution A; taking out and transferring the solution to a solution B, adding an acidic catalyst to adjust the pH value of the solution to be 3, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, circularly reacting for 1-3 times, filtering, washing and drying to obtain a composite membrane A; transferring the mixture into a solution C, setting the temperature to be 0-5 ℃ under vibration, dropwise adding the solution D, and setting the temperature to be 50 ℃ after dropwise adding to react for 2-3 hours; and taking out and transferring the membrane to a solution E, setting the temperature to be 60 ℃ under vibration, reacting for 1-1.5 hours, washing and filtering to obtain the polyethylene composite membrane.

According to the technical scheme, a microporous polyethylene film is taken as a main body, hydrophilic polyvinyl alcohol and bacterial cellulose are used for modifying the film to increase hydrophilicity, then the hydrophilic polyvinyl alcohol and the bacterial cellulose are crosslinked to form a high-strength compact film layer on the microporous polyethylene film, then a thiol-ene click reaction is generated by using a thiol bond on L-cysteine, L-cysteine with amino and carboxyl is grafted in a pore channel of the microporous polyethylene film, and the antifouling property of the film is increased. The prepared polyethylene composite membrane has good durability and repeated utilization rate.

Microporous polyethylene membranes are a good main body of water treatment membranes due to adjustable pores, excellent mechanical properties, chemical stability, and are widely used in battery separators, but they are rarely used for water treatment because: (1) it is hydrophobic; (2) the mechanical capacity is easy to be reduced when the water-based paint is operated in a water environment for a long time, so that the durability is low and the service life is short; (3) after long-term use, the pollution residues block the pore channels, so that the water treatment efficiency is reduced, and the water treatment quality is reduced. Therefore, a series of treatments is required to increase hydrophilicity, water resistance, and antifouling property, thereby making it durable for water treatment.

The specific treatment process is as follows: (1) the microporous polyethylene membrane is soaked in an ethanol solution, the surface tension of the membrane is reduced, the PVA (polyvinyl alcohol) solution with the optimal concentration and the bacterial cellulose solution are convenient to diffuse on the membrane, the solution with the lower concentration is uniformly dispersed on the surface of the microporous polyethylene membrane through a circulating filtration process under a cross-flow membrane filter, the blockage problem of the pore channel of the microporous polyethylene membrane is inhibited, and the pore structure is ensured. (2) Placing the PVA and the bacterial cellulose in a microwave reactor, forming a polyvinyl alcohol/bacterial cellulose crosslinking network under the crosslinking of a crosslinking agent tartaric acid, wherein the PVA and the bacterial cellulose both contain a large amount of similar hydroxyl groups and can generate hydrogen bonding, and the covalent bond formed by the PVA and the bacterial cellulose ensures that the composite film has good heat resistance, water resistance and better mechanical strength; and microwave reaction crosslinking is adopted in the process, compared with common heat crosslinking, the reaction time is short, the crosslinking degree is higher, the reaction is uniform, and pore channels which are uniformly distributed and have similar sizes are formed by crosslinking. In addition, crosslinking increases the strength of the composite film, increases the thickness of the film layer, and roughens the surface of the composite film, and the roughness causes residual dirt to adhere, so that the antifouling property is reduced, and therefore, the addition of micromolecular acryloyl chloride is needed to reduce the surface roughness. Simultaneously, crosslinked polyvinyl alcohol/bacterial cellulose, in water treatment process, but the inside PVA of pore is in water treatment process, some groups can dissociate out the network on the macromolecular chain, electrified group is mutual repulsion, make the macromolecular chain expand, enlarge the crosslinked network, the effectual dirt that blocks, but too much inflation can make the aperture reduce, the infiltration descends, the flux reduces, so bacterial cellulose has been added in the crosslinked network, it has the effectual degree of expansion that has reduced polyvinyl alcohol/bacterial cellulose, certain flux has been guaranteed. Meanwhile, the bacterial cellulose has higher crystallinity and a fine network, and the mechanical properties such as tensile strength and the like are effectively enhanced. (3) The membrane is firstly dipped in triethylamine and hydroquinone solution with optimal concentration, the triethylamine is used as a catalyst, the hydroquinone is used as a polymerization inhibitor, and then acryloyl chloride is dripped to react acyl chloride with hydroxyl on polyvinyl alcohol/bacterial cellulose, so that unsaturated bonds are grafted on the composite membrane, and simultaneously, the roughness of the surface of the composite membrane is reduced and the antifouling property is increased. (4) The L-cysteine is a substance containing amino, carboxyl and thiol groups, and due to the reactions such as crosslinking, grafting and the like, the abundance of the hydroxyl groups is reduced, so that the hydrophilicity is reduced, the amino of the L-cysteine can increase the hydrophilicity, and the carboxyl and protein pollutants in the water body can generate electrostatic repulsion, so that the antifouling property is increased; meanwhile, the amino group has positive charge and the carboxyl group has negative charge, and the amino group and the carboxyl group form a hydration layer in the composite membrane, so that the adhesion of pollutants is effectively inhibited. And through the click reaction of thiol-alkene, the L-cysteine is grafted on the pore and the surface of the composite membrane, so that the reactive amino and carboxyl on the L-cysteine are not lost due to the grafting reaction.

Compared with the prior art, the invention has the following beneficial effects: (1) the polyvinyl alcohol/bacterial cellulose is used for modifying the microporous polyethylene film, so that the heat resistance, the water resistance and the mechanical strength of the polyethylene composite film are improved; (2) the polyvinyl alcohol/bacterial cellulose is prepared by a microwave reaction method, so that the reaction time is reduced, and the polyvinyl alcohol/bacterial cellulose has a more uniform and more detailed cross-linking structure; (3) the polyvinyl alcohol/bacterial cellulose is modified by utilizing micromolecular acryloyl chloride, the surface roughness of the polyethylene composite membrane is reduced, the smoothness of the membrane is increased, and therefore the attachment of pollutants is reduced. (4) L-cysteine is grafted on the polyethylene composite membrane by utilizing thiol reaction, so that the reaction of active amino and carboxyl is effectively inhibited, and the antifouling property of the composite membrane is improved. (5) The swelling of polyvinyl alcohol is utilized to increase the antifouling property of the film and achieve a synergistic effect with L-cysteine.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

step 1: preparation of a solvent: mixing a PVA solution with the concentration of 0.8 wt% and a bacterial cellulose solution with the concentration of 0.5 wt% according to the volume ratio of 2:1, and stirring for 1.25 hours at the temperature of 92 ℃ to obtain a solution A for later use; mixing 6 wt% sulfuric acid solution and 0.28 wt% tartaric acid solution in equal volume, and stirring at 28 deg.C for 42 min to obtain solution B; mixing a triethylamine solution with the concentration of 2 wt%, a hydroquinone solution with the concentration of 3 wt% and a lauryl sodium sulfate solution with the concentration of 0.15 wt% in equal volume to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D with the concentration of 1.5 wt% for later use; dissolving L-cysteine and potassium persulfate in a mass ratio of 12.5:1 in a buffer solution to obtain a solution E with the concentration of 22 wt% for later use;

step 2: preparing a polyethylene composite film: soaking the microporous polyethylene membrane in an ethanol solution for 13 minutes, transferring to a cross-flow membrane filter, setting the temperature at 23 ℃ and the pressure at 5bar, and circularly filtering for 10 minutes by using the solution A; taking out and transferring the solution to a solution B, adding an acidic catalyst to adjust the pH value of the solution to 3, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, circularly reacting for 2 times, filtering, washing and drying to obtain a composite membrane A; transferring the solution into a solution C, setting the temperature to be 3 ℃ under vibration, dropwise adding the solution D, and setting the temperature to be 50 ℃ after dropwise adding to react for 2.5 hours; taking out and transferring the membrane into a solution E, setting the temperature at 60 ℃ under vibration, reacting for 1.25 hours, washing and filtering to obtain the polyethylene composite membrane.

Example 2:

step 1: preparation of a solvent: mixing a PVA solution with the concentration of 0.5 wt% and a bacterial cellulose solution with the concentration of 0.4 wt% according to the volume ratio of 2:1, and stirring for 1 hour at 90 ℃ to obtain a solution A for later use; mixing 5 wt% sulfuric acid solution and 0.25 wt% tartaric acid solution in equal volume, and stirring at 25 deg.C for 40 min to obtain solution B; mixing a triethylamine solution with the concentration of 1 wt%, a hydroquinone solution with the concentration of 2 wt% and a lauryl sodium sulfate solution with the concentration of 0.1 wt% in equal volume to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D with the concentration of 1 wt% for later use; dissolving L-cysteine and potassium persulfate in a mass ratio of 12:1 in a buffer solution to obtain a solution E with the concentration of 20 wt% for later use;

step 2: preparing a polyethylene composite film: soaking the microporous polyethylene membrane in ethanol solution for 10 minutes, transferring to a cross-flow membrane filter, setting the temperature at 20 ℃ and the pressure at 5bar, and circularly filtering for 8 minutes by using the solution A; taking out and transferring the solution to a solution B, adding an acidic catalyst to adjust the pH value of the solution to 3, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, circularly reacting for 1 time, filtering, washing and drying to obtain a composite membrane A; transferring the solution into a solution C, setting the temperature to be 0 ℃ under vibration, dropwise adding the solution D, and setting the temperature to be 50 ℃ after dropwise adding to react for 2 hours; taking out and transferring the membrane to a solution E, setting the temperature to be 60 ℃ under vibration, reacting for 1 hour, washing and filtering to obtain the polyethylene composite membrane.

Example 3:

step 1: preparation of a solvent: mixing a PVA solution with the concentration of 1 wt% and a bacterial cellulose solution with the concentration of 0.6 wt% according to the volume ratio of 2:1, and stirring for 1.5 hours at 95 ℃ to obtain a solution A for later use; mixing 8 wt% sulfuric acid solution and 0.3 wt% tartaric acid solution in equal volume, and stirring at 30 deg.C for 45 min to obtain solution B; mixing a triethylamine solution with the concentration of 3 wt%, a hydroquinone solution with the concentration of 4 wt% and a lauryl sodium sulfate solution with the concentration of 0.2 wt% in equal volume to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D with the concentration of 2 wt% for later use; dissolving L-cysteine and potassium persulfate in a mass ratio of 13:1 in a buffer solution to obtain a solution E with the concentration of 25 wt% for later use;

step 2: preparing a polyethylene composite film: soaking the microporous polyethylene membrane in an ethanol solution for 15 minutes, transferring to a cross-flow membrane filter, setting the temperature at 25 ℃ and the pressure at 5bar, and circularly filtering for 12 minutes by using the solution A; taking out and transferring the solution to a solution B, adding an acidic catalyst to adjust the pH value of the solution to 3, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, circularly reacting for 3 times, filtering, washing and drying to obtain a composite membrane A; transferring the solution into a solution C, setting the temperature to be 5 ℃ under vibration, dropwise adding the solution D, and setting the temperature to be 50 ℃ after dropwise adding to react for 3 hours; taking out and transferring the membrane into a solution E, setting the temperature at 60 ℃ under vibration, reacting for 1.5 hours, washing and filtering to obtain the polyethylene composite membrane.

Example 4: the concentration of the PVA solution is changed to 10 wt%, and the concentration of the bacterial cellulose solution is changed to 6 wt%; otherwise, the same as example 1;

example 5: no bacterial cellulose is added; otherwise, the same as example 1;

example 6: no acryloyl chloride was added; otherwise, the same as example 1;

example 7: replacing L-cysteine with serine methacrylate, setting the temperature at 60 ℃, reacting for 18 hours, and grafting on the polyethylene composite membrane; otherwise, the same as example 1;

experiment: the strength polyethylene composite membrane for water treatment prepared in the embodiment 1-7 is used for carrying out various characterizations: (1) performing water flux characterization by using pure water to obtain water flux A; adopting 500ppm BSA (bovine serum albumin) aqueous solution to carry out anti-pollution test to obtain BSA retention rate, cleaning the polyethylene composite membrane after filtering the protein aqueous solution, and then representing by pure water to obtain water flux B; (2) according to a GB/T1040.3-2006 standard method, a universal mechanical tester is adopted to characterize the tensile strength of the polyethylene composite film; (3) according to the GB/T30447-2013 standard method, a contact angle tester is adopted to represent the contact angle of the polyethylene composite film; (4) characterizing the surface roughness of the surface of the polyethylene composite film by adopting a scanning electron microscope; all data are shown in the following table:

examples

Water flux A

Water flux B

Retention rate of BSA

Tensile strength

Contact angle

Surface roughness

Example 1

598.7L/h·m²

586.7L/h·m²

89％

167MPa

66°

20.53nm

Example 2

589.2L/h·m²

577.4L/h·m²

85％

165MPa

68°

21.02nm

Example 3

592.5L/h·m²

581.6L/h·m²

87％

160MPa

67°

20.89nm

Example 4

498.2L/h·m²

489.7L/h·m²

83％

172MPa

61°

25.23nm

Example 5

513.1L/h·m²

497.4L/h·m²

86％

145MPa

60°

24.99nm

Example 6

580.3L/h·m²

562.8L/h·m²

62％

156MPa

70°

25.84nm

Example 7

536.4L/h·m²

509.58L/h·m²

79％

166MPa

69°

21.56nm

And (4) conclusion: from the data of examples 1 to 3, it is shown that: the prepared polyethylene composite membrane has good hydrophilicity and excellent tensile strength which can reach 167 MPa; the surface roughness is about 20nm, and the smoothness is better. The retention rate of BSA is as high as 89%, the BSA has excellent anti-fouling property, and the water flux is 585L/h.m²Above, the flux recovery rate after cleaning reaches 98%, and the flux recovery rate has cyclic usability.

Comparing the data of example 4 with the data of example 1, it can be found that: the concentration of the PVA solution and the bacterial cellulose solution is improved, the flux is reduced, the tensile strength is increased, the contact angle is reduced, the roughness is increased, and the retention rate of BSA is the reason that: the excessively high concentration increases the crosslinking degree, partially blocks the pore channels of the polyethylene composite membrane, so that the flux is reduced, but the loading capacity is increased, so that the mechanical performance is improved; and the surface roughness is increased so that the hydrophilicity is increased; the retention rate of BSA also decreased slightly because the swelling property of PVA polymer chains increased the antifouling property, but the increased roughness made the accumulation of contaminants easier.

Comparing the data of example 5 with the data of example 1, it can be seen that: the decrease in tensile strength, the decrease in flux, is due to: PVA and bacterial cellulose both contain a large amount of similar hydroxyl groups, and can generate hydrogen bonding, and the covalent bond formed by the PVA and the bacterial cellulose ensures that the composite film has good heat resistance, water resistance and better mechanical strength; and microwave crosslinking is used in the process, compared with ordinary thermal crosslinking, the reaction time is short, the crosslinking degree is higher, the reaction is uniform, and pore channels formed by crosslinking are uniformly distributed and have similar sizes. The flux reduction is due to the swelling properties of PVA, which makes the pores smaller.

Comparing the data of example 6 with the data of example 1, it can be seen that: the surface roughness increased and the BSA rejection decreased due to: the polyvinyl alcohol/bacterial cellulose is modified by the micromolecular acryloyl chloride, so that the surface roughness of the polyethylene composite membrane can be effectively reduced, the smoothness of the membrane is increased, the attachment of pollutants is reduced, and the antifouling property is increased.

Comparing the data of example 7 with that of example 1, it can be seen that: the rejection rate is reduced, the flux is reduced, and the abundance of zwitterions can be reduced without grafting the polymer with zwitterions by thiol-ene click reaction, so that the rejection rate is reduced. And other products can be generated by grafting in a thermal crosslinking mode, so that the polyethylene composite membrane is crosslinked with substances on the polyethylene composite membrane, the pore diameter is reduced, and the flux is reduced.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a high-strength polyethylene composite membrane for water treatment is characterized by comprising the following steps: the method comprises the following steps:

step 1: preparation of a solvent: mixing the PVA solution and the bacterial cellulose solution to obtain a solution A for later use; mixing a sulfuric acid solution and a tartaric acid solution to obtain a solution B for later use; mixing a triethylamine solution, a hydroquinone solution and a sodium dodecyl sulfate aqueous solution to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D for later use; dissolving L-cysteine and potassium persulfate in a buffer solution to obtain a solution E for later use;

step 2: preparing a polyethylene composite film: soaking the microporous polyethylene membrane in an ethanol solution, transferring the microporous polyethylene membrane into a cross-flow membrane filter, and circularly filtering for 8-12 minutes by using the solution A; taking out and transferring the solution to a solution B, adjusting the pH value of the solution to be 3 by using an acidic catalyst, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, filtering, washing and drying to obtain a composite membrane A; transferring the mixture into a solution C, dropwise adding a solution D, and setting the temperature to be 50 ℃ for reaction after the dropwise adding is finished; and taking out and transferring the solution to the solution E, setting the temperature to be 60 ℃ for reaction under vibration, washing and filtering to obtain the polyethylene composite membrane.

2. The preparation method of the high-strength polyethylene composite membrane for water treatment according to claim 1, characterized in that: the thickness of the polyethylene composite film is 150-300 mu m.

3. The preparation method of the high-strength polyethylene composite membrane for water treatment according to claim 1, characterized in that: the specific process of the step 1 is as follows: mixing the PVA solution and the bacterial cellulose solution according to the volume ratio of 2:1, and stirring for 1-1.5 hours at the temperature of 90-95 ℃ to obtain a solution A for later use; mixing a sulfuric acid solution and a tartaric acid solution in equal volume, and stirring for 40-45 minutes at the temperature of 25-30 ℃ to obtain a solution B for later use; mixing a triethylamine solution, a hydroquinone solution and a sodium dodecyl sulfate solution in equal volume to obtain a solution C for later use; dissolving acryloyl chloride in toluene to obtain a solution D for later use; dissolving L-cysteine and potassium persulfate in a mass ratio of (12-13): 1 in a buffer solution to obtain a solution E for later use.

4. The preparation method of the high-strength polyethylene composite membrane for water treatment according to claim 3, characterized in that: the concentration of the PVA solution is 0.5-1 wt%; the concentration of the bacterial cellulose solution is 0.4-0.6 wt%; the concentration of the sulfuric acid solution is 5-8 wt%; the tartaric acid solution accounts for 0.25-0.3 wt%; the concentration of the triethylamine is 1-3 wt%; the concentration of the hydroquinone solution is 2-4 wt%; the concentration of the sodium dodecyl sulfate solution is 0.1-0.2 wt%.

5. The preparation method of the high-strength polyethylene composite membrane for water treatment according to claim 3, characterized in that: the concentration of the solution D is 1-2 wt%; the concentration of the solution E is 20-25 wt%.

6. The preparation method of the high-strength polyethylene composite membrane for water treatment according to claim 1, characterized in that: the specific process of the step 2 is as follows: soaking the microporous polyethylene membrane in an ethanol solution for 10-15 minutes, transferring the microporous polyethylene membrane into a cross-flow membrane filter, setting the temperature to be 20-25 ℃ and the pressure to be 5bar, and circularly filtering the microporous polyethylene membrane for 8-12 minutes by using the solution A; taking out and transferring the solution to a solution B, adding an acidic catalyst to adjust the pH value of the solution to be 3, placing the solution in a microwave reactor, setting the power to be 500W, reacting for 2 minutes, circularly reacting for 1-3 times, filtering, washing and drying to obtain a composite membrane A; transferring the mixture into a solution C, setting the temperature to be 0-5 ℃ under vibration, dropwise adding the solution D, and setting the temperature to be 50 ℃ after dropwise adding to react for 2-3 hours; and taking out and transferring the membrane to a solution E, setting the temperature to be 60 ℃ under vibration, reacting for 1-1.5 hours, washing and filtering to obtain the polyethylene composite membrane.